1. Field of the Invention
The present invention relates to an unnecessary vibration detection apparatus and a driving control apparatus of a vibration type actuator.
2. Description of the Related Art
An ultrasonic motor that is a kind of vibration type actuator is mounted on a copy machine, interchangeable lenses for cameras, and the like.
In recent years, together with high performance of equipment and low power consumption, high rotation precision, high efficiency and the like have been required.
The ultrasonic motor enables a low-speed high torque driving compared to an electromagnetic motor which is represented by a DC (direct-current) brushless motor. However, some problems exist so as to meet the above requirements.
For example, depending on a contact state between a stator that is configured by an elastic body and a piezoelectric element, and a body to be driven (for example, a rotor that is a moving body), there is a case where movements are not stabilized to generate unnecessary vibrations which causes an abnormal noise, a speed irregularity or an uneven wear.
As a countermeasure to the abnormal noise and the speed irregularity depending on the contact state, Japanese Patent Application Laid-Open No. H02-026284 discloses a driving method of cancelling an audible frequency signal, which separately selects the audible frequency signal of the vibration and thereafter feeds it back. More specifically, a circuit configuration has been proposed, in which only an audible frequency is allowed to pass through by the use of a band pass filter.
However, the vibration type actuator in the related art described above has the following problems.
First, when the band pass filter was configured using a passive element, there was a case in which characteristics of the filter could not be changed, could not be coped with a changed component of the audible sound, and thus an effect only for a predetermined particular component could be obtained.
In addition, a phase delay of the detected signal could not be ignored and thereby such an adverse effect was also present due to insertion of the filter.
In addition, a complex circuit configuration was required and therefore, there is room for improvement in terms of cost.